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Bessel function of order one.


double x, y, j1();
y = j1(x);


Returns a Bessel function of order one of the argument.
The domain is divided into the intervals [0, 8] and (8, infinity). In the first interval a 24 term Chebyshev expansion is used. In the second, the asymptotic trigonometric representation is employed, using two rational functions of degree 5/5.


                      Absolute error:
arithmetic   domain      # trials      peak         rms
    DEC       0, 30       10000       4.0e-17     1.1e-17
    IEEE      0, 30       30000       2.6e-16     1.1e-16